Home automation has been growing for many years. Home automation includes lighting control, heating, ventilation and air-conditioning (HVAC) control, remote controlled sprinkler for irrigation, intelligent alarm system etc. Wireless home automation has gained its popularity in recent years in part due to its relative easy installation in comparison to a hardwired one. These wireless devices require wiring for power, if they are not operated by battery. Compared to hardwired home automation system, many wireless home automation systems aim for Do-It-Yourself market because they typically can be installed easily. There are specific wireless protocols developed for home automation, such as Z-wave™, ZigBee™ Insteon™ etc. One popular application for wireless home automation system is lighting control. Among all lighting control devices, wall switch controlled lightings are perhaps the most popular because these switches are installed in millions of buildings and most lighting in residential houses are operated by wall switches. Therefore the demand for wall switch operated lighting control in home automation field is very high.
In order to convert a traditional wall switch to one that can be controlled wirelessly, a wall switch module is required. A wall switch module replaces an existing wall switch. Such wall switch module includes a wireless receiver to receive signal from a controller such as a remote control, and typically also has relay or triac output to control brightness or lighting on/off. Wall switch module requires alternating current (AC) power to operate. Typical operating current for a wall switch module is around 10 mA-20 mA. One AC power supply would come from the live and neutral connections of household power supply. However, most wall switch boxes do not have a neutral connection. Generally only 2 wires are fed into a wall switch box: a live feed from the AC power supply to the switch, and a wire extending from the switch to a load. In most cases, the other side of the load is connected directly to the neutral of the AC power supply without returning to the switch box. In other words, a typical switch box is provided with only a live feed but no neutral to connect to a wall switch module to complete the circuit. To run a neutral wire back to such a switch box tends to be costly if such neutral wire was not installed in the first place. This is due to the limited access to existing wirings. Therefore, there is a need for a wall switch module that can operate with the existing wirings in the switch box, even without a neutral connection.
It is known to provide lighting control products for wall switch control without a neutral connection. Such a wall switch module itself is treated as a load, connected in series with the load to be switched, which would be turned on partially in order to conduct current but the current conducted therethrough is kept at minimum so the load is still practically kept in an “off” state. The wall switch module must operate with this minimal current. In order to turn on a conventional incandescent load, such as a tungsten bulb, a required current must flow through the load. For example, the required current is around 40 mA for a 10 W bulb. For a conventional incandescent bulb and with a current less than 40 mA, the bulb would remain in the off state. The wall switch module could draw a current as much as 30 mA to maintain its operation without switching on the tungsten bulb. However, compact fluorescent light (CFL) tends to be much more sensitive to the conducted current. With only 200 μA flowing through, a compact fluorescent light could flash randomly instead of remain in the off state. Thus, only 200 μA, far below the threshold for switching on a tungsten bulb, could have undesirable impact to the normal operation of CFL. This makes it difficult or not possible to have the wall switch module to draw current the same way if the load is a compact fluorescent load. Recently, compact fluorescent lamp is becoming more popular due to its low energy consumption compared to traditional tungsten bulb. Some countries have already indicated gradual phase out of tungsten bulbs. Thus, there is a need to have a wall switch module for replacing a conventional switch but without having undesirable impact on the normal operation of CFL and fluorescent light.
There is a need for an improved design of wall switch which can work on various different types of loads, such as incandescent load, fluorescent load, CFL, even motor loading etc, without the need to have a neutral connection.
The forgoing creates challenges and constraints for a wall switch for replacing a conventional wall switch. There is therefore a need for an improved wall switch as compared to the existing art. It is an object of the present invention to mitigate or obviate at least one of the above mentioned disadvantages.